Almost perfect.
The gameplay and graphics reminds me much of Another World. I liked it a lot, but it leaves too many unanswered questions; enough to actually force the player to come up with his or her own conclusion (which can be fun sometimes, but I'd rather know what the creator thinks in this case). I've drawn my own conclusions as to -why- this all happened, and about the sister and everything, but what do you think?
Regardless, I'd like to see more puzzle/thriller-like games in the future, great job!